The present invention relates to weft knitted spacer fabrics and, more particularly, to jacquard pattern weft knitted spacer fabrics knitted on double knit or jersey circular knitting machines, and methods of knitting such fabrics.
Weft knitted spacer fabrics include two knitted layers, that is, a front or face weft knitted layer and a back weft knitted layer, disposed in spaced relationship and coupled together by a network of spacer or distance yarns. The spacer yarns are typically firmer and more resilient than the yarns of the face and back layers so that the spacer yarns maintain the spacing between the two weft knitted layers. The resilient nature of the spacer yarns enables the front and back layers to be compressed together and then recover, thereby giving the spacer material resiliency in the thickness direction. Moreover, by knitting the face and back layers with the resilient yarns, the spacer fabric may be given stretch and recovery properties in the longitudinal and lateral directions of the fabric. Such spacer fabrics are used for moldable and non-moldable textile materials in the production of wearing apparel and medical, automotive, household and technical textiles.
Spacer fabrics are knitted on double jersey circular knitting machines having rotatable needle cylinders and needle dials. The cylinder knitting needles are arranged to reciprocate axially in grooves in the periphery of the cylinder between welt, tuck and knit positions and the needles of the dial reciprocate in radial grooves in the latter between welt, tuck and knit positions. When in the knit positions, the heads of the cylinder and dial needles are disposed on the circumference of an imaginary circle about the upper end of the needle cylinder. The cylinder knits the face layer of the spacer fabric and the dial knits the back layer and, at the same time, a spacer yarn is connected into the two layers by the cylinder and dial needles in order to couple the layers together.
A double jersey circular knitting machine may be set up for two different modes of operation in which the positional relationships of the cylinder and dial needles differ. In one mode, referred to as the rib gating position or mode, the cylinder needles and dial needles are alternately arranged such that the paths of travel of the dial needles do not intersect with the paths of travel of the cylinder needles and vice versa. In the other mode of operation, referred to as the interlock gating position or mode, the cylinder and dial needles are arranged with their paths of travel respectively in common planes so that the paths of travel intersect.
Jacquard pattern weft knitted spacer fabrics have hitherto been knitted on double jersey circular knitting machines set up for knitting in the rib gating mode so that the heads of the cylinder needles selected for travel to the knit positions will not collide with the heads of the dial needles also selected for travel to the knit positions and the cylinder and dial needles advance past each other. Needle collision cannot therefore occur in jacquard knitting on a circular knitting machine set up for rib gating.
However, needle collision is a distinct problem when jacquard knitting on a double jersey circular knitting machine set up for interlock gating. Hence, the jacquard knitting of spacer fabrics has been restricted to circular knitting machines set up for rib gating. This has several disadvantages. For example, the fabric compressibility, in the thickness direction, is limited. Also, the spacer yarns tend to push through the cylinder knit jacquard face fabric and the dial knit back layer.
One aspect of the present invention is the provision of a jacquard pattern weft knitted spacer fabric which has improved compressibility and recovery properties and in which the spacer yarn is less visible and there is less possibility of the spacer yarn emerging through either of the weft knitted layers of the fabric.
One aspect of the present invention is the provision of a method of knitting a jacquard pattern weft knitted spacer fabric on a double jersey circular knitting machine having a rotatable needle cylinder and needle dial, with the method including the steps of adjusting the cylinder and dial to knit in an interlock gating mode in which the cylinder and dial needles reciprocate between welt, tuck and knit positions respectively in substantially common planes, weft knitting a jacquard pattern layer on the needle cylinder, weft knitting a plain layer on the needle dial, and coupling the two layers together by a spacer yarn which is connected in each layer on alternate needles of the cylinder or dial, as the case may be, traveling to the tuck position for capturing the spacer yam, thereby to hook the spacer yam about the necks of cooperating stitches of the weft knitted layers.
In accordance with one aspect of the present invention, the resulting jacquard pattern weft knitted spacer fabric may include a jacquard pattern face layer weft knitted on the needle cylinder and a plain back layer weft knitted on the dial, these two layers being mutually spaced apart and coupled together by a network of spacer yarns which are firmer and more resilient than the yarns of the face and back layers. Moreover, the connecting points at which the spacer yarn connects with the weft knitted layers are such that, in opposing courses of the two layers, the connecting points of one layer are substantially centralized between two connecting points of the other layer. The spacer yarn therefore has a more upright stitch formation than spacer fabrics hitherto knitted on double-jersey circular knitting machines set up for rib gating, and this enables thicker spacer fabrics to be produced having better compression, springiness and recovery properties. Such fabric characteristics are particularly important for end uses, such as car seats, office and domestic furniture and mattress tickings.
In accordance with one aspect of the present invention, the spacer yarn is preferably less visible than in spacer fabrics knitted on machines set up for rib gating. This is because the interlock gating knitted structure provides better cover and, therefore, less possibility of the spacer yarns emerging through either the cylinder knitted jacquard face layer or the dial knitted back layer. Hence, the visual and tactile aesthetics of the spacer fabric of the present invention are preferably not impaired by exposure of the spacer yarn.
According to one aspect of the present invention, the stretch and recovery characteristics and properties, moldability, wear abrasion, moisture management, breathability, electrical properties and TOG rating can be specifically engineered to meet the demands of a particular end use. This is achieved by careful selection of the types of yarns and fibers used on the face and back of the fabric, the type and thickness of the spacer or distance yarn, inclusion of a filler or inlay yarn, and also by the inclusion or otherwise of varying percentages of stretch polyester, polyamide and polyurethane yarns, such as the range of elastane yarns marketed under the trade mark xe2x80x9cLycraxe2x80x9d by Dupont Textiles and Interiors. The use of stretch polyester, stretch polyamide and polyurethane yarns, such as, Lycra elastane yarns, enables the raised effect of a jacquard pattern to be enhanced as well as the stretch and recovery characteristics of the spacer fabric.
Conveniently, the jacquard pattern weft knitted spacer fabric according to the invention can be produced on a double jersey circular knitting machine of the type described in EP-A-0 591 987 which is adjusted for knitting in the interlock gating mode. Such a circular knitting machine includes a rotating knitting cylinder having axial grooves in its outer periphery with a knitting needle positioned in each groove. The cylinder needles reciprocate upwardly and downwardly in the cylinder grooves between welt, tuck and knit positions under the control of cylinder needle operating cams disposed about the cylinder, in conjunction with intermediate and lower jacks which are disposed in the cylinder grooves beneath the cylinder needles and one below the other. There are two different sets of intermediate and lower jacks disposed in alternate cylinder grooves below the associated cylinder needles. The intermediate jacks of the two sets differ from one another only in the height of the butts thereon which engage cooperating cylinder cams controlling movement of the intermediate jacks. They are referred to as high and low butt intermediate jacks, respectively, in the sense that the butt on one intermediate jack is above the other in relation to the vertical axis of the cylinder. In a similar sense, the lower jacks have armatures of different heights and are referred to as high armature and low armature jacks. The intermediate and lower jacks with the same type of butt or armature, that is high or low, are disposed in the same cylinder groove. The intermediate jacks are reciprocated upwardly and downwardly in the cylinder grooves between bottom, welt and tuck positions by cooperation of their butts with dual race intermediate jack cams. The lower jacks are reciprocated upwardly and downwardly in the cylinder grooves between bottom and welt positions by cooperation of their butts with lower jack cams.
The cylinder needles are controlled via the intermediate and lower jacks, by a needle selection and operating mechanism which selects the cylinder needles for movement from the welt position to the knit or tuck positions for knitting a jacquard pattern. The mechanism includes the lower jack cams for raising selected lower jacks from their bottom positions to the welt positions, and an electronic selection mechanism for selectively moving, into the path of the lower jack cams, the lower jacks in the cylinder grooves containing the cylinder needles selected for movement to the knit or tuck positions so that the selected lower jacks are raised from their bottom positions to the welt position and the selected lower jacks raise the associated corresponding intermediate jacks from their bottom positions to the welt positions. The intermediate jack cams selectively raise, from the welt position to the tuck position, only those intermediate jacks which are below cylinder needles selected for movement to the knit positions. Needle cams are provided for raising to the knit positions cylinder needles raised to the tuck position by the jacks, if the pattern dictates such movement.
Slidably mounted in the dial grooves of the knitting machine, in alternate grooves, are two different types of dial needle having butts in differing positions. These are referred to as high butt and low butt needles in the sense that the high butts are radially outwardly of the low butts. The dial needles are selectively reciprocated in the dial grooves by dual cam tracks which control the two different types of butts of the dial needles selectively to move the dial needles from welt positions to tuck or knit positions or maintain the dial needles in their welt positions.
With the machine construction described in EP-A-0 591 987, even if wrong needle selection is made, as frequently occurs for one reason or another, the lower jacks wrongfully selected can move only from the bottom to the welt position. The intermediate jack cam system includes an upper guard cam and a lower guard cam and an intermediate jack raising cam which is selectable for operation or non-operation position. The intermediate jack raising cam for a wrongfully selected needle will be in the non-operating position and will not engage the butt of the intermediate jack moved upwardly by a wrongfully selected lower jack and will not move the intermediate jack further upwardly beyond the welt position. Similarly, the needle raising cam will not engage the butt of the cylinder needle and will not move the cylinder needle above the welt position. Therefore, needle collision is obviated in this circular knitting machine set-up for interlock gating operation.
When the above-described machine is operated to produce a spacer fabric according to the present invention, at those yarn feeders where the jacquard pattern face layer is produced by the cylinder needles, the individual cylinder needle selection may be varied and combined so as to produce distinctly different visual and aesthetic effects. For example, flat surface jacquard designs can be produced based on individual cylinder needles being selected to either knit or miss. If, however, the cylinder needles are selected in knit and tuck combinations, it is possible to produce jacquard designs having raised surface effects.